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Date: Mon, 30 Mar 2020 16:19:51 -0700
From: "Paul E. McKenney" <paulmck@...nel.org>
To: Will Deacon <will@...nel.org>
Cc: linux-kernel@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>,
Jann Horn <jannh@...gle.com>, Kees Cook <keescook@...omium.org>,
Maddie Stone <maddiestone@...gle.com>,
Marco Elver <elver@...gle.com>,
Peter Zijlstra <peterz@...radead.org>,
Thomas Gleixner <tglx@...utronix.de>, kernel-team@...roid.com,
kernel-hardening@...ts.openwall.com
Subject: Re: [RFC PATCH 07/21] Revert "list: Use WRITE_ONCE() when adding to
lists and hlists"
On Tue, Mar 24, 2020 at 03:36:29PM +0000, Will Deacon wrote:
> This reverts commit 1c97be677f72b3c338312aecd36d8fff20322f32.
>
> There is no need to use WRITE_ONCE() for the non-RCU list and hlist
> implementations.
>
> Cc: Paul E. McKenney <paulmck@...nel.org>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Signed-off-by: Will Deacon <will@...nel.org>
Which means that the lockless uses of hlist_empty() will also need
attention, correct?
Thanx, Paul
> ---
> include/linux/list.h | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/list.h b/include/linux/list.h
> index ec1f780d1449..c7331c259792 100644
> --- a/include/linux/list.h
> +++ b/include/linux/list.h
> @@ -70,7 +70,7 @@ static inline void __list_add(struct list_head *new,
> next->prev = new;
> new->next = next;
> new->prev = prev;
> - WRITE_ONCE(prev->next, new);
> + prev->next = new;
> }
>
> /**
> @@ -843,7 +843,7 @@ static inline void hlist_add_head(struct hlist_node *n, struct hlist_head *h)
> n->next = first;
> if (first)
> first->pprev = &n->next;
> - WRITE_ONCE(h->first, n);
> + h->first = n;
> n->pprev = &h->first;
> }
>
> @@ -858,7 +858,7 @@ static inline void hlist_add_before(struct hlist_node *n,
> n->pprev = next->pprev;
> n->next = next;
> next->pprev = &n->next;
> - WRITE_ONCE(*(n->pprev), n);
> + *(n->pprev) = n;
> }
>
> /**
> --
> 2.20.1
>
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